This application is the National Phase of International Application PCT/JP01/00306 filed Jan. 18, 2001 which designated the U.S. and that International Application was published under PCT Article 21(2) in English.
The present invention relates to an oil amount detector for detecting an amount of lubrication oil in a case of a compressor, a refrigeration apparatus and an air conditioner wherein the oil amount detector is attached.
A compressor such as an air conditioner attached on a refrigeration apparatus is covered with a case so that a refrigerant is sucked into the case and the sucked refrigerant is compressed to and discharged to the outside. Lubrication oil is filled in the case. A part of the lubrication oil flows into the refrigerating cycle together with the refrigerant as the compressor discharges the refrigerant. Consequently, it sometimes happen that the supply of the lubrication oil becomes insufficient in the compressor. When the supply of the lubrication oil becomes insufficient, a sliding portion comes to run out of the oil, which exerts an unfavorable influence upon the life of the compressor.
As means for coping with such disadvantage, there is known a float switch style oil surface adjuster as shown in Jpn. Pat. Appln. KOKAI Publication No. 5-164417. This oil surface adjuster takes in lubrication oil in the case into a vessel by means of an even oil tube to detect an oil surface (an oil amount) with a vertical movement of a float floating on a surface inside of the vessel.
On the other hand, as means for bringing back into the case of the compressor the lubrication oil discharged together with the refrigerant from the compressor, there is known an oil separator. For example, in the invention disclosed in Japanese Unexamined Patent Publication No. 4-184048, the oil separator is provided on piping on the side of discharging the refrigerant of the compressor, so that the lubrication oil discharged together with the refrigerant is caught with the oil separator and the lubrication oil which is retained in the oil separator is brought back to the piping of on the side of sucking the refrigerant of the compressor in the case where the supply of the lubrication oil becomes insufficient in the compressor.
Like the float switch style oil surface adjuster, when the oil separator detects the oil surface with a mechanical float switch, a trouble is likely to be generated. Furthermore, when the compressor is suspended, the refrigerant is liquefied to be retained in the case of the compressor, and the piping of the refrigerating cycle. In this case, the liquid refrigerant is mixed into the lubrication oil so that the lubrication oil is dissolved with the result that the oil surface in the case has risen to the position higher than the actual amount. In such a situation, in the above oil surface adjuster, an ostensible oil surface including the liquid refrigerant is detected so that an accurate detection of the oil surface cannot be made. In actuality, even when the supply of the lubrication oil is insufficient, the operation of the compressor continues as it is. In the end, an unfavorable influence is exerted to the life of the compressor is some cases.
On the other hand, in an example of the oil separator, a long time is required until a predetermined amount (an oil return amount required for the maintenance of the oil surface of the compressor) of the lubrication oil is retained in the oil separator next after the lubrication oil retained in the oil separator is once brought back to the compressor. Consequently the shortage of the lubrication oil in the compressor cannot be swiftly settled which, in the end, exerts an unfavorable influence to the life of the compressor. There is also a problem in that the capacity of the oil separator becomes large in order to secure a sufficient oil replacement amount for the maintenance of the oil surface of the compressor with the result that the separator itself becomes large.
The present invention has been made in view of the above circumstances, and an object of the invention is to precisely detect an amount of oil in the case of the compressor in good reliability without using a mechanical switch.
The present invention provides an oil amount detector of a compressor which has a case in which lubrication oil is filled, and which sucks and compresses the refrigerant and discharges the refrigerant from the case, the detector comprising:
an oil holding tank communicated to the case;
a pressuring pipe for introducing part of the refrigerant discharged from the compressor into a oil holding tank for use in pressurization for allowing oil to flow out from the oil holding tank;
a return pipe for allowing oil flowing out of the oil holding tank to return to the case
a first temperature sensor for detecting a temperature of the refrigerant which introduced to the oil holding tank;
a second temperature sensor for detecting a temperature of oil which flowing out from the oil holding tank; and
detection means for detecting an oil amount in the case from a comparison between the detected temperature of the first temperature sensor and the detected temperature of the second temperature sensor.